1. Field of the Invention
The present invention relates to a multiplexing method, a multiplexing apparatus and a network including the multiplexing apparatus, and especially relates to the multiplexing method and the apparatus that multiplex a plurality of data streams and output to an arbitrarily selected circuit and the network including the multiplexing apparatus.
2. Description of the Related Art
A time division switch (called TSW hereinafter) not only multiplexes two or more data streams but also often performs cross-connect processing that outputs the multiplexed data to an arbitrarily selected circuit.
FIG. 1 shows a block diagram of an example of a multiplexing apparatus 10. A conventional multiplexing apparatus 10 includes a low-speed multiplexing unit 20 which multiplexes low-speed data supplied from terminal units and outputs to a transmission path 28, and a cross-connect unit 30 which performs a cross-connect process of the data supplied from the transmission path 28.
The low-speed multiplexing unit 20 and the cross-connect unit 30 assign addresses to the terminal unit, the circuit, and the transmission, path 28, and have access control memory units 25 and 33 (henceforth ACM), respectively, that store information about relations between the addresses. The TSW 24 and 32 perform the multiplexing and the cross-connect process using the ACM 25 and ACM 33.
Technical progress in recent years has realized an economical high-speed and large-capacity TSW. Accordingly, one TSW unit can now replace the TSW 24 and 32 of FIG. 1.
FIG. 2 shows a block diagram of another example of a multiplexing apparatus 12. The multiplexing apparatus 12 of FIG. 2 replaces the TSW 24 and TSW 32 with one unit of TSW 40, thereby the low-speed multiplexing unit 20 and the cross-connect unit 30 are combined into one unit. In addition, ACM42 assigns addresses to terminal units and circuits, and stores information about relations between the addresses.
However, since the multiplexing apparatus 10 of FIG. 1 includes the two TSWs, namely TSW 24 and TSW 32, there is a problem that delay increases. Moreover, since the two ACMs, namely ACM 25 and ACM 33 are required, synchronization of the ACMs is necessary to attain correct operations.
On the other hand, the multiplexing apparatus 12 of FIG. 2 is structured with one each of TSW (the TSW40) and ACM (the ACM42), avoiding the problems of the delay and the synchronization as in the case with the multiplexing apparatus 10 of FIG. 1. However, there emerges another problem in that user convenience in circuit operations is facilitated if the multiplexing process and the cross-connect process are separated. That is, when a user operates a circuit, it is easier to manage the two processes separately, one for multiplexing and the other for cross-connect using two TSWs.